A method and device for measuring and calculating the contact angle of a droplet

Abstract

The present invention discloses a method for measuring and calculating the contact angle of a liquid droplet, comprising the following steps: dropping a liquid droplet with a mass of M and a density of ρ onto a horizontally placed transparent slide; obtaining a front projection image of the liquid droplet on the slide and measuring the radius of the front projection image, denoted as r; comparing the magnitudes of M and ; if, then calculating the value of H through the equation, where V is the volume of the liquid droplet, H is the height of the liquid droplet, and calculating the contact angle between the liquid droplet and the slide; if calculating the value of H through the equations and R = r, where V is the volume of the liquid droplet, H is the height of the liquid droplet, and R is the radius of the sphere where the liquid droplet is located, and calculating the contact angle between the liquid droplet and the slide. The measurement and calculation method eliminates the cumbersome and costly horizontal adjustment platform. Most importantly, accurate and reliable measurement and calculation results can be obtained even when the liquid droplet is small or the reflectivity of the liquid droplet is low.

Description

Technical Field

[0001] The present invention relates to the technical field of measurement for characterizing the wetting properties of interfaces, and particularly relates to a method and device for measuring and calculating the contact angle of a liquid droplet. Background Art

[0002] When a liquid contacts a solid, the liquid will spread outwards along the solid surface. At the same time, the original solid-gas interface and liquid-gas interface in the system are gradually replaced by a new solid-liquid interface. This process is called wetting. The degree of wetting of the liquid on the solid surface is called the wettability of the solid surface.

[0003] Wettability is one of the important characteristics of a solid surface and plays an important role in industrial and agricultural production and people's daily lives, such as oil extraction, pesticide spraying, and fabric waterproofing and washing. Surface wettability mainly depends on the surface roughness and surface free energy of the solid, and its magnitude is usually measured by the contact angle between the liquid droplet and the solid surface. At the equilibrium state, tangents to the solid and liquid surfaces are made respectively at the three-phase junction of the solid, liquid, and gas. The angle formed by the two tangents inside the liquid is the contact angle.

[0004] Among traditional contact angle measurement methods, the liquid cake height method and the spherical cap measurement method are more commonly used. Among them, in the liquid cake height method, liquid is continuously added to a liquid droplet placed on a solid plane until the liquid droplet only increases the area of the solid-liquid contact surface without increasing the height, forming a liquid cake; in the spherical cap measurement method, a micro liquid droplet is placed on the solid surface to form an ideal spherical cap shape. However, in actual operation, it is very difficult to form an ideal liquid cake or spherical cap shape, resulting in inaccurate measurement results.

[0005] With the popularization of digital cameras and the improvement of resolution, methods for calculating the contact angle based on the captured liquid droplet images are increasingly adopted. The measurement process is as follows: the liquid droplet is photographed to obtain an image of the liquid droplet, and then after obtaining the edge of the liquid droplet in the obtained image of the liquid droplet, a polynomial fitting is used to obtain the curve equation at the gas-liquid-solid junction. Among them, the liquid-solid junction (the interface between the liquid droplet and the sample) is used as the baseline, and the gas-liquid junction (the interface between the liquid droplet and the air) is fitted to form the liquid droplet edge curve. The contact angle can be easily obtained based on the liquid droplet edge curve and the baseline. It requires a small amount of liquid droplets, simple experimental operation, and later uses a computer to fit the surface contour of the liquid droplet, greatly improving the measurement accuracy. However, there are also certain limitations. The characteristic of this measurement method is to directly frame the image horizontally along the sample surface. When the liquid droplet is small or the reflectivity of the liquid droplet is low, insufficient light reflection cannot be provided, and there will be a large error in the imaging of the liquid droplet edge, resulting in a multiple increase in the final measurement error. Moreover, when photographing the liquid droplet, it is required that the photographing lens be strictly horizontal with the liquid droplet, which requires a precise and costly horizontal adjustment platform and skilled operation techniques. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method and device for measuring and calculating the contact angle of a liquid droplet, aiming at the disadvantages of the prior art. The measurement and calculation method or device can directly calculate the size of the contact angle based on the radius of the contact surface between the liquid droplet and the carrier sheet and the mass of the liquid droplet, eliminating the cumbersome and costly horizontal adjustment platform. Most importantly, accurate and reliable measurement and calculation results can be obtained even when the liquid droplet is small or the reflectivity of the liquid droplet is low.

[0007] To solve the above technical problem, the present invention provides a method for measuring and calculating the contact angle of a liquid droplet, characterized in that the measurement and calculation method includes the following steps:

[0008] Drop a liquid droplet with a mass of M and a density of ρ onto a horizontally placed transparent carrier sheet;

[0009] Obtain the orthographic projection image of the liquid droplet on the carrier sheet and measure the radius of the orthographic projection image, denoted as r;

[0010] Compare M with ;

[0011] If , then calculate the value of through the equation H , where V is the volume of the liquid droplet, H is the height of the liquid droplet, and calculate the contact angle between the liquid droplet and the carrier sheet;

[0012] If , calculate the values of and through the equations H , where V is the volume of the liquid droplet, H is the height of the liquid droplet, R is the radius of the sphere where the liquid droplet is located, and calculate the contact angle between the liquid droplet and the carrier sheet.

[0013] In the method for measuring and calculating the contact angle of a liquid droplet provided by the present invention, the step of "dropping a liquid droplet with a mass of M and a density of ρ onto a horizontally placed transparent carrier sheet" includes:

[0014] Using a liquid droplet injection module to drop N liquid droplets with a density of ρ onto a weighing module, and the weighing module measures the mass of N drops of the liquid droplets as M ;

[0015] Use the droplet injection module to drop N drops of the droplet liquid onto a horizontally placed transparent slide.

[0016] In the method for measuring and calculating the contact angle of a droplet provided by the present invention, the orthographic projection image of the droplet and the slide is obtained by an image acquisition module, and the image acquisition module includes an image sensor, a telecentric lens, and a reflector.

[0017] In the method for measuring and calculating the contact angle of a droplet provided by the present invention, the telecentric lens is installed parallel to the horizontal plane on the image sensor, the reflector is arranged directly below the slide, and the reflector has a reflecting surface at an angle of 45° to the horizontal plane.

[0018] In the method for measuring and calculating the contact angle of a droplet provided by the present invention, a vibration isolation module is connected to the bottom of the weighing module.

[0019] Correspondingly, the present invention also provides a device for measuring and calculating the contact angle of a droplet. The measuring and calculating device includes a droplet injection module, a horizontally placed transparent slide, an image acquisition module, and a calculation module; wherein,

[0020] The droplet injection module is used to drop a droplet with a mass of M and a density of ρ onto the slide;

[0021] The image acquisition module is used to obtain the orthographic projection image of the droplet on the slide and measure the radius of the orthographic projection image, denoted as r;

[0022] The calculation module is used to compare M with ;

[0023] The calculation module is also used to, when , calculate the value of through the equation H , where V is the volume of the droplet, H is the height of the droplet, and calculate the contact angle between the droplet and the slide;

[0024] The calculation module is also used to, when , calculate the value of and through the equation H , where V is the volume of the droplet, H is the height of the droplet, R is the radius of the sphere where the droplet is located, and calculate the contact angle .

[0025] In the droplet contact angle measurement and calculation device provided by the present invention, the measurement and calculation device further includes a weighing module; the droplet injection module is used to drop N droplets with a density of ρ on the weighing module and then on the slide; the weighing module is used to measure the mass of N droplets, denoted as M .

[0026] In the droplet contact angle measurement and calculation device provided by the present invention, the image acquisition module includes an image sensor, a telecentric lens, and a reflector.

[0027] In the droplet contact angle measurement and calculation device provided by the present invention, the telecentric lens is installed parallel to the horizontal plane on the image sensor, the reflector has a reflecting surface at an angle of 45° with the horizontal plane, and the reflecting surface is located below the slide and in front of the telecentric lens.

[0028] In the droplet contact angle measurement and calculation device provided by the present invention, a vibration isolation module is connected to the bottom of the weighing module.

[0029] Compared with the prior art, implementing the droplet contact angle measurement and calculation method provided by the present invention has the following beneficial effects: The measurement and calculation method includes the following steps: Drop a droplet with a mass of M and a density of ρ on a horizontally placed transparent slide; obtain a front projection image of the droplet on the slide and measure the radius of the front projection image, denoted as r; compare M with ; if , then calculate the value of through the equation H , where V is the volume of the droplet, H is the height of the droplet, and calculate the contact angle between the droplet and the slide; if , calculate the value of and through the equations H , where V is the volume of the droplet, H is the height of the droplet, R is the radius of the sphere where the droplet is located, and calculate the contact angle between the droplet and the slide. Thus, the measurement and calculation method eliminates the complicated and costly horizontal adjustment platform. Most importantly, accurate and reliable measurement and calculation results can be obtained even when the droplet is small or the reflectivity of the droplet is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1Schematic diagram of the contact angle between the droplet and the slide when ;

[0031] Figure 2 Schematic diagram of the contact angle between the droplet and the slide when ;

[0032] Figure 3 Schematic structural diagram of the second embodiment of the present invention.

[0033] Explanation of the reference numerals in the drawings in the specific implementation manners:

[0034] Specific implementation manners

[0035] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific implementation manners of the present invention will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment 1

[0037] This embodiment provides a method for measuring and calculating the contact angle of a droplet. The measurement and calculation method includes the following steps:

[0038] Step S1: Drop a droplet with a mass of M and a density of ρ onto a horizontally placed transparent slide 3. In this embodiment, step S1 is implemented in two steps, namely step S11 and step S12. Step S11 is to drop N droplets with a density of ρ onto the weighing module by using the droplet injection module 1, and the weighing module measures the mass of N droplets as M. Step S12 is to drop N droplets onto the horizontally placed transparent slide 3 by using the droplet injection module 1. Specifically, N is a natural number greater than or equal to 1. For example, it can be 1, 2, 3, 4, etc. The droplet injection module 1 is an injection valve, and its single-point volume is at the μL level, and the volume of each droplet ejected is the same. Therefore, dropping the same number of droplets on the weighing module and the slide 3 by using the droplet injection module 1 can ensure that the mass of the droplets on the weighing module is equal to the mass of the droplets on the slide 3. In order to accurately weigh the mass of N droplets, the weighing module in this embodiment uses an electronic micro weighing instrument, which can be used to measure the mass at the mg level. Moreover, the bottom of the weighing module 2 is connected to a vibration isolation module 4 to reduce the influence of the outside world on the weighing accuracy of the weighing module 2.

[0039] Step S2: Obtain the orthographic projection image of the droplet on the slide 3, and measure the radius of the orthographic projection image, denoted as r. In this embodiment, the orthographic projection image of the droplet on the slide 3 is obtained by an image acquisition module, and the image acquisition module includes an image sensor 5, a telecentric lens 6, and a reflector 7. The telecentric lens 6 is installed parallel to the horizontal plane on the image sensor 5, the reflector 7 is arranged directly below the slide 3, and the reflector 7 has a reflecting surface at an angle of 45° with the horizontal plane. Specifically, the image sensor 5 uses a CCD (Charge Coupled Device), and installing the telecentric lens 6 on the image sensor 5 can avoid image parallax errors caused by distance. The slide 3 is parallel to the induction light emitted by the image sensor 5. The induction light emitted by the image sensor 5 irradiates parallel to the horizontal plane on the reflecting surface of the reflector 7 through the telecentric lens 6, and after being reflected by the reflecting surface, it irradiates perpendicularly to the horizontal plane on the slide 3, thereby obtaining the orthographic projection image of the droplet on the slide 3.

[0040] Step S3: Compare M with In this embodiment, step S3 is completed by a calculation module, and the calculation module can be a personal computer or other devices with data operation and processing capabilities. We can input the value of M, the value of r, and ρ the value into the calculation module, and the calculation module can complete the step of comparing M with .

[0041] Step S4: If , then calculate the value of through the equation H , where V is the volume of the droplet, H is the height of the droplet, and calculate the contact angle between the droplet and the slide 3. Specifically, when , it indicates that the contact angle between the droplet and the slide 3 is less than 90°, as shown in Figure 1 , Figure 1 is a schematic diagram of the contact angle between the droplet and the slide 3 when . In Figure 1 , point A is the intersection of the contour line of the droplet and the contour line of the slide 3, line L1 passes through point A and is tangent to the contour line of the droplet, point B is the intersection of the radius of the sphere where the droplet is located perpendicular to the slide 3 and the slide 3, and point O is the center of the sphere of the sphere where the droplet is located. Then the volume VIt can be expressed by the volume formula of a spherical segment, and can also be expressed by dividing the mass by the density, so that we can obtain the equation , obviously, we can calculate H through the above equation. The contact angle between the droplet and the carrier sheet 3 θ = ∠ AOB . It is not difficult to obtain from Figure 1 that , where R is the radius of the sphere where the droplet is located. Also, because we can know from Figure 1 that , so we can obtain , and then obtain , that is, , and then obtain the contact angle . In this embodiment, the step S4 is also completed by the calculation module.

[0042] Step S5, if , calculate the value of through the equation and H , where V is the volume of the droplet, H is the height of the droplet, R is the radius of the sphere where the droplet is located, and calculate the contact angle between the droplet and the carrier sheet 3. Specifically, when , it indicates that the contact angle between the droplet and the carrier sheet 3 is greater than 90°. Refer to Figure 2 , Figure 2 is a schematic diagram of the contact angle between the droplet and the carrier sheet 3 when . In Figure 2 , point E is the intersection point of the contour line of the droplet and the contour line of the carrier sheet 3. The straight line L2 passes through point E and is tangent to the contour line of the droplet. Point D is the intersection point of the radius of the sphere where the droplet is located perpendicular to the carrier sheet 3 and the carrier sheet 3. Point C is the center of the sphere of the sphere where the droplet is located. Then the volume V of the droplet can be expressed by subtracting the volume of the spherical segment that can form a complete sphere with the droplet from the volume of the sphere where the droplet is located, and can also be expressed by dividing the mass by the density, so that we can obtain the equation . Also, when When it indicates that the contact angle between the droplet and the carrier 3 is greater than 90°, that is to say, the volume of the droplet is greater than half of the volume of the sphere where the droplet is located. Obviously, at this time, the radius r of the orthographic projection image of the droplet on the carrier 3 is the radius R of the sphere where the droplet is located, that is, at this time R = r. Through the above two equations, we can calculate and obtain H the value of. As Figure 2 shown, the contact angle between the droplet and the carrier 3 , α is also equal to ∠ ECD . It is not difficult to obtain from Figure 2 that , then the contact angle . In this embodiment, the step S5 is also completed by the calculation module.

[0043] In summary, according to the method for measuring and calculating the contact angle of a droplet provided in this embodiment, only the radius of the contact surface between the droplet and the carrier 3 and the mass of the droplet need to be measured to directly calculate the size of the contact angle. The complicated and costly horizontal adjustment platform used in the existing contact angle measurement method is omitted. Most importantly, accurate and reliable measurement and calculation results can also be obtained when the droplet is small or the reflectivity of the droplet is low.

[0044] Embodiment 2

[0045] This embodiment provides a device for measuring and calculating the contact angle of a droplet. Referring to Figure 3 , the measuring and calculating device includes a droplet injection module 1, a weighing module 2, a vibration isolation module 4, a horizontally placed transparent carrier 3, an image acquisition module, a calculation module, and a base 9. The image acquisition module includes an image sensor 5, a telecentric lens 6, and a reflector 7. The telecentric lens 6 is installed on the image sensor 5 parallel to the horizontal plane. The vibration isolation module 4, the reflector 7, and the image sensor 5 are all arranged on the base. The reflector 7 is placed between the vibration isolation module 4 and the image sensor 5. The weighing module 2 is fixedly connected to the upper side of the vibration isolation module 4. The carrier 3 is arranged above the reflector 7. The upper surface of the carrier 3 and the upper surface of the weighing module 2 are on the same horizontal plane. The droplet injection module 1 is movably installed horizontally on a track above the weighing module 2 and the carrier 3, and the droplet outlet of the droplet injection module 1 faces vertically downward.

[0046] The droplet injection module 1 is used to drop N droplets with a density of ρ on the weighing module 2 and the carrier 3 successively; the weighing module 2 is used to measure the mass of N droplets, denoted as M. Specifically, N is a natural number greater than or equal to 1. For example, it can be 1, 2, 3, 4, etc. The droplet injection module 1 is a spray valve with a single-point volume at the μL level, and the volume of each droplet ejected is consistent. Therefore, dropping the same number of droplets on the weighing module and the carrier 3 using the droplet injection module 1 can ensure that the mass of the droplets on the weighing module is equal to the mass of the droplets on the carrier 3. In order to accurately weigh the mass of N droplets, the weighing module in this embodiment uses an electronic micro weighing instrument, which can be used to measure the mass at the mg level. Moreover, a vibration isolation module 4 is connected to the bottom of the weighing module 2 to reduce the influence of the outside world on the weighing accuracy of the weighing module 2.

[0047] The image acquisition module includes an image sensor 5, a telecentric lens 6, and a mirror 7. The telecentric lens 6 is installed parallel to the horizontal plane on the image sensor 5, and the mirror 7 is arranged directly below the carrier 3. The mirror 7 has a reflecting surface at an angle of 45° to the horizontal plane. Specifically, the image sensor 5 uses a CCD (Charge Coupled Device), and installing the telecentric lens 6 on the image sensor 5 can avoid the image parallax error caused by the distance. The carrier 3 is parallel to the induction light emitted by the image sensor 5. The induction light emitted by the image sensor 5 is irradiated on the reflecting surface of the mirror 7 parallel to the horizontal plane through the telecentric lens 6, and after being reflected by the reflecting surface, it is irradiated on the carrier 3 perpendicular to the horizontal plane, so as to obtain a front view of the contact surface between the droplet and the carrier 3.

[0048] The calculation module can be a personal computer or other devices with data operation and processing capabilities. The calculation module is used to calculate the contact angle between the droplet and the carrier 3 according to the values of M, r, and ρ.

[0049] The process of using the measurement and calculation device to measure the contact angle between the droplet and the carrier 3 is described in detail below.

[0050] 1) Use the droplet injection module 1 to drop N droplets with a density of ρ on the weighing module, and the weighing module measures the mass of N droplets as M.

[0051] 2) Use the droplet injection module 1 to drop N droplets on the horizontally placed transparent carrier 3.

[0052] 3) Turn on the image sensor 5 to obtain the front projection image of the droplet on the carrier 3, and measure the radius of the front projection image, denoted as r.

[0053] 3) The calculation module compares M with Size.

[0054] 4) If , the calculation module calculates the value of through the equation H , where V is the volume of the droplet, H is the height of the droplet, and the contact angle between the droplet and the slide 3 is calculated. Specifically, when , it indicates that the contact angle between the droplet and the slide 3 is less than 90°. See Figure 1 . Figure 1 is a schematic diagram of the contact angle between the droplet and the slide 3 when . In Figure 1 , point A is the intersection of the contour line of the droplet and the contour line of the slide 3. The straight line L1 passes through point A and is tangent to the contour line of the droplet. Point B is the intersection of the radius perpendicular to the slide 3 of the sphere where the droplet is located and the slide 3. Point O is the center of the sphere where the droplet is located. Then the volume V of the droplet can be expressed by the volume formula of a spherical segment and can also be expressed as the mass divided by the density. Thus, we can obtain the equation . Obviously, we can calculate the value of H through the above equation. The contact angle θ between the droplet and the slide 3 = ∠ AOB . It is not difficult to obtain Figure 1 from . In the formula, R is the radius of the sphere where the droplet is located. Also, because we can know from Figure 1 that , so we can get , and then obtain , that is, , and then obtain the contact angle .

[0055] 5) If , the calculation module calculates the value of and through the equations H , where V is the volume of the droplet, H is the height of the droplet, R is the radius of the sphere where the droplet is located, and the contact angle between the droplet and the slide 3 is calculated. Specifically, when , it indicates that the contact angle between the droplet and the slide 3 is greater than 90°. See Figure 2 . Figure 2Schematic diagram of the contact angle between the droplet and the slide 3 when In Figure 2 , point E is the intersection of the contour line of the droplet and the contour line of the slide 3. The straight line L2 passes through point E and is tangent to the contour line of the droplet. Point D is the intersection of the radius perpendicular to the slide 3 of the sphere where the droplet is located and the slide 3. Point C is the center of the sphere where the droplet is located. Then the volume V of the droplet can be expressed by subtracting the volume of the spherical segment that can form a complete sphere with the droplet from the volume of the sphere where the droplet is located. At the same time, it can also be expressed by dividing the mass by the density. Thus, we can obtain the equation . Also, when , it indicates that the contact angle between the droplet and the slide 3 is greater than 90°. That is to say, the volume of the droplet is greater than half of the volume of the sphere where the droplet is located. Obviously, at this time, the radius r of the orthographic projection image of the droplet on the slide 3 is the radius R of the sphere where the droplet is located, that is, R = r at this time. Through the above two equations, we can calculate the value of H . As shown in Figure 2 , the contact angle between the droplet and the slide 3 α is also equal to ∠ ECD . It is not difficult to obtain Figure 2 from . Then the contact angle .

[0056] In summary, during the process of measuring the contact angle using the droplet contact angle measurement and calculation device provided in this embodiment, only the radius of the contact surface between the droplet and the slide 3 and the mass of the droplet need to be measured to directly calculate the size of the contact angle. The complicated and costly horizontal adjustment platform in the existing contact angle measurement device is omitted. Most importantly, accurate and reliable measurement and calculation results can also be obtained when the droplet is small or the reflectivity of the droplet is low.

[0057] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the present invention and the claims. These all belong to the protection scope of the present invention.

Claims

1. A method for measuring and calculating the contact angle of a liquid droplet, characterized in that, the measuring and calculating method comprises the following steps: Drop a liquid droplet with a mass of M and a density of ρ onto a horizontally placed transparent slide; Obtain the orthographic projection image of the liquid droplet on the slide, and measure the radius of the orthographic projection image, denoted as r; Compare M with in terms of magnitude; If , then the value of is calculated through the equation H , where V is the volume of the droplet, H is the height of the droplet, and the contact angle between the droplet and the slide is calculated; If , the value of and is calculated through the equations H . Among them, V is the volume of the droplet, H is the height of the droplet, R is the radius of the sphere where the droplet is located, and the contact angle between the droplet and the slide is calculated 2. The method for measuring and calculating the contact angle of a liquid droplet according to claim 1, characterized in that, The step of "dropping a liquid droplet with a mass of M and a density of ρ onto a horizontally placed transparent slide" comprises: Using a droplet injection module, N droplets with a density of ρ are dropped onto a weighing module, and the weighing module measures the mass of N droplets of the liquid droplets as M ; Use the liquid droplet injection module to drop N drops of the liquid on a horizontally placed transparent slide.

3. The method for measuring and calculating the contact angle of a liquid droplet according to claim 1, characterized in that, the orthographic projection image of the liquid droplet and the slide is obtained by an image acquisition module, and the image acquisition module includes an image sensor, a telecentric lens and a reflector.

4. The method for measuring and calculating the contact angle of a liquid droplet according to claim 3, characterized in that, the telecentric lens is installed parallel to the horizontal plane on the image sensor, the reflector is arranged directly below the slide, and the reflector has a reflecting surface at an angle of 45° to the horizontal plane.

5. The method for measuring and calculating the contact angle of a liquid droplet according to claim 2, characterized in that, the bottom of the weighing module is connected to a vibration isolation module.

6. A device for measuring and calculating the contact angle of a liquid droplet, characterized in that, the measuring and calculating device includes a liquid droplet injection module, a horizontally placed transparent slide, an image acquisition module and a calculation module; wherein, The droplet injection module is used to drop droplets with a mass of M , a density of ρ onto the carrier slide; the image acquisition module is used to obtain the orthographic projection image of the liquid droplet on the slide, and measure the radius of the orthographic projection image, denoted as r; The calculation module is used to compare M with in terms of magnitude; The calculation module is further configured to, when , calculate the value of through the equation H , where V is the volume of the droplet, H is the height of the droplet, and calculate the contact angle between the droplet and the slide; The calculation module is further configured to, when , calculate the value of and through the equations H . Wherein, V is the volume of the droplet, H is the height of the droplet, R is the radius of the sphere where the droplet is located, and calculate the contact angle between the droplet and the slide.

7. The device for measuring and calculating the contact angle of a liquid droplet according to claim 6, characterized in that, The measurement and calculation device further includes a weighing module; the droplet injection module is used to drop N droplets with a density of ρ onto the weighing module and then onto the slide; the weighing module is used to measure the mass of N droplets of the liquid droplets, denoted as M .

8. The device for measuring and calculating the contact angle of a liquid droplet according to claim 6, characterized in that, the image acquisition module includes an image sensor, a telecentric lens and a reflector.

9. The device for measuring and calculating the contact angle of a liquid droplet according to claim 8, characterized in that, the telecentric lens is installed parallel to the horizontal plane on the image sensor, the reflector has a reflecting surface at an angle of 45° to the horizontal plane, and the reflecting surface is located below the slide and in front of the telecentric lens.

10. The device for measuring and calculating the contact angle of a liquid droplet according to claim 7, characterized in that, the bottom of the weighing module is connected to a vibration isolation module.

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